We set up an appointment with the woman, posing as interested clients to confirm that she was performing the procedures as advertised.

Through the messaging app, a consultation was quickly booked that very night.

We happened to catch her at the door of her three-room flat as she was coming home from dinner. She greeted us warmly in Mandarin.

She said she had been staying there for two months with her Singaporean husband and one-year-old child.

The chatty 30-year-old Chinese national also revealed that she was a permanent resident and had been doing cosmetic procedures since 2011.

"My clients are mainly from China. I'm used to them coming around 2am or 3am, after their work. They're mostly KTV girls, and sometimes the sessions can last until daybreak," she said, explaining why she was able to meet us at night.

Inside the flat, the living area was furnished with a flat-screen television, a black couch and a dining table. Children's toys littered a play mat on the floor.

The woman would later confirm that the couch served as an "operating table", where all procedures, including double-eyelid surgery, took place.

Next to the couch, there was a small plastic rack filled with bottles of medicine, gauze and alcohol swabs.

On the dining table, between a roll of cling wrap and containers of Chinese New Year goodies, was her silver "tool box".

The woman, who was dressed casually in a blue blouse and black pants with her hair in a messy bun, claimed she was a nurse in China and was trained to administer injections.

She showed us certificates which she claimed were from institutes in South Korea and China that said she was a "plastic practice physician" with qualifications in "micro-plastic surgery".

However, nothing showed up when we checked these institutes online.

When asked if she knew what she was doing was illegal, she said her husband intended to help her apply for a licence with the Ministry of Health that will allow her to practise in Singapore, but had not done so.

During the hour-long consultation, she was patient and detailed in explaining the different procedures offered.

Korean-imported Botox injections start from $300 a shot, but she offered us a discounted price of $650 for three shots.

A slimming injection, which came from vials labelled "V Line-A solution", was similarly priced and would help to dissolve fatty tissues, she said.

"There are no side effects. But before we do the injection, we'll do a test on your hand and inject (the chemical)," she said.

While most licensed clinics charge about $4,000 for incision-method double-eyelid surgery, she charges just $2,000.

She said: "I do (the surgery) very carefully... Other people might take an hour or so, but I take four hours. It's the face after all - a tiny mistake would affect the client greatly."

Most of her clients come for slimming injections for the face and, according to her, were satisfied with the results.

She also assured us that the procedures were safe, having done the various injections on herself multiple times.

On another visit the next day, we asked the woman about the cosmetic procedures in her home, but she declined to comment and directed the queries to her husband.

DENIED

But the Singaporean construction site manager, who wanted to be known only as Kelvin, 46, denied that his wife was doing cosmetic procedures at home.

He said she was a housewife who used to sell clothes. He accused his wife's friends in China of making up stories to malign her.

But when he was shown pictures of his wife at home next to the silver "tool box", he changed his tune. He said his wife's friends would occasionally come over to do facials, but added that "no needles were involved".

"Sometimes I would ask my friends to buy facial products from Japan and Korea too," he said.

Kelvin said his wife has to take care of their one-year-old child and his 80-year-old mother.

"I'm home on the weekends and at night. If she was really running a business, I would definitely know it," he said.

When we checked the woman's WeChat account last Friday, all the pictures and advertisements had been deleted.

Two of the woman's neighbours who moved into the estate about a month ago, said they were unaware of her home-run cosmetic clinic.

I do (the surgery) very carefully... Other people might take an hour or so, but I take four hours. It's the face after all - a tiny mistake would affect the client greatly.

- The woman, who charges $2,000 for incision-method double-eyelid surgery, while most licensed clinics charge $4,000

Only trained docs can do procedures

Plastic surgeons The New Paper spoke to were shocked by the cosmetic procedures the woman claimed to have done in her HDB flat.

Plastic surgeon Martin Huang said: "If she doesn't have a medical degree, it's clearly illegal. Because firstly, you need to be a doctor, and secondly, you need to have training in these procedures."

Dr Huang, who has over 20 years' experience in the industry, also serves as Singapore's National Secretary in the International Society of Aesthetic Plastic Surgery.

Besides the lack of qualifications and proper training, the environment where the procedures take place is also a cause for concern, added another plastic surgeon, Dr Tan Ying Chien.

Said Dr Tan: "The environment needs to be extremely clean to minimise the chances of infection, and such conditions are definitely not found in an HDB flat."

Over the years, Dr Tan has seen patients who come to him for help after botched cosmetic jobs, usually administered by beauticians or doctors who are not qualified.

Their conditions include bad reactions or infections after being injected with unapproved chemicals, unnatural or asymmetrical double eyelids, and even nose implants that have protruded through the skin.

He said: "I advise people not to go to these questionable 'clinics'. It might be very cheap but when something goes wrong, the person won't be able to correct things for you.

"Any form of invasive treatment performed on the human body should be taken seriously."

NOT ALLOWED IN HDB FLATS

When contacted, an HDB spokesman said: "Medical practices, services or procedures are subject to specific licensing requirements by the relevant medical governing bodies, hence they are not allowed in HDB flats."

A Ministry of Health (MOH) spokesman said invasive aesthetic procedures like cosmetic surgery and filler injections are to be performed only by trained registered medical practitioners.

To protect the interest and safety of consumers, MOH will take stern action against unqualified persons who provide medical treatment.